FIG. 4 is a longitudinal sectional view of a conventional semiconductor laser device. Reference numeral 10 is a semiconductor laser element, reference numeral 11 is an LD (laser diode), reference numeral 12 is an active layer, reference numeral 13 is a Cr layer, reference numeral 14 is an Au layer, reference numeral 15 is an Au layer, reference numeral 16 is an Au—Ge layer, reference numeral 17 is an Au layer, reference numeral 30 is a metal base, reference numeral 31 is a metal block, and reference numeral 40 is a conductive adhesive. In order to radiate the heat that is generated in the active layer 12, the semiconductor laser element 10 is attached to the metal base 30 by the conductive adhesive 40. The metal base 30 functions as a heat sink.
FIG. 5 is a longitudinal sectional view of a different semiconductor laser device. This device is disclosed in Japanese Patent Application Laid-open No. S59-31085. In this device, in order to radiate the heat generated from a light 12 shown in FIG. 4, a silicon submount 20 is inserted between the semiconductor laser element 10 and the metal base 30, and each of these are constituted by brazing with a gold and silicon brazing material 50 and 60. Note that the silicon submount 20 is made from a heat sink with a thermal expansion coefficient close to the material constituting the semiconductor laser element.